Symbol: Blanc's Magnifying Glass
Aside from the fact that Blanc's Magnifying glass serves as a comedic element, it is symbolic of the deeper and darker layers that surround Harlan's death.
Symbol: Knives
The knives prominently featured in the film are symbolic not only of the Thrombeys' insincerity, but also of the violent actions that Ransom takes.
Symbol: Marta's Coffee Mug
The coffee mug that Marta inherited that says "My House, My Rules, My Coffee" is symbolic not only of Marta's newfound wealth and power, it is symbolic of Marta's goodness and her kindness and her empathy despite all that she had to endure.
Motif: Marta's Funeral Invitiation
The most common motif in the film is the Thrombey family mentioning that they wanted to invite Marta to Harlan's funeral but were "overruled." This underscores the Thrombey family's insincerity and shows just how little they care about Marta and her troubles.
Allegory: Politics
Although it may seem like a simple murder-mystery, Knives Out is a political allegory that discusses issues dealing with immigration, the entitlement of the wealthy, and the hypocrisy of (some) liberals.
